Medical equipment for radiation therapy treats tumorous tissue with high energy radiation. The dose and the placement of the dose must be accurately controlled to insure both that the tumor receives sufficient radiation to be destroyed, and that damage to the surrounding and adjacent non-tumorous tissue is minimized. Intensity modulated radiation therapy (“IMRT”) treats a patient with multiple rays of radiation each of which may be independently controlled in intensity and/or energy. The rays are directed from different angles about the patient and combine to provide a desired dose pattern. In external source radiation therapy, a radiation source external to the patient treats internal tumors. The external source is normally collimated to direct a beam only to the tumor location. Typically, the radiation source consists of either high-energy X-rays, electrons from certain linear accelerators, or gamma rays from highly focused radioisotopes.
One way to control the position of the radiation delivered to the patient is through the use of a patient support device, such as a couch, that is adjustable in one or more directions. Similar patient support devices are also used in computed tomography (“CT”) scanning devices and Magnetic Resonances Imagers (“MRIs”). The patient support device allows the patient to be moved into and out of a field of radiation and in some cases, allows for adjustments of patient position during a radiation treatment session.